"JIMMIE" wrote in message
...
I came across an old single LPDA TV antenna in the trask. It was
pretty much FUBAR except for a coupe of feet of boom matrial and a few
insulators. My XYL is into making models and castings and she can make
a mold of the insulators easy enough. I was wondering if anyone knew
of a good casting material that would be compatable with the
requirements to build a single boom LPDA antenna to form the
insulators. She is not usually concerned with strength or UV
resistance so she couldnt help much on this part.
Epoxy and polyester resins come to mind. If you are rebuilding the TV
antenna and not adding significant weight, these should work well. Use the
low viscosity resins sold in quarts, and not epoxy glues.
For added strength, consider adding chopped fiberglass strands. For
reduced weight, glass microballoons may be added to the resins. They are
extremely light with a specific gravity of 0.18 to 0.25 depending on the
manufacturer. Phenolic microballoons are also available.
For ultraviolet protection, a small amount of titanium dioxide may be added
(1 to 5%), but the microballoons will do a fair job alone. Painting the
finished insulators with acrylic paint (KrylonŽ) will also provide good UV
resistance.
Many marine supply stores carry these resins, the chopped fiberglass, and
the microballoons. Be extra careful with the polyester catalyst (typically
methyl-ethyl-ketone peroxide) as it is extremely damaging to the eyes.
Good luck with your project.
73, Dr. Barry L. Ornitz WA4VZQ
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